There are various technical areas in which it is necessary to reliably adjust a fairly small distance between two parallel surfaces. One example can be found in U.S. Pat. No. 4,168,522, which relates to a copying machine exposure device in which an original is conveyed between two flat glass plates. To avoid imaging errors, the original must be kept flat between the glass plates, with little freedom of movement in the direction perpendicular to the direction of conveyance. This requires accurate adjustment of the small distance between the two glass plates within close tolerances.
There are various devices for measuring the small distance between two parallel surfaces. For example, French patent application No. 2,309,833 shows a sensing device based on the capacitive principle. U.S. Pat. No. 3,239,938 shows a sensing device working with a strain gage while U.S. Pat. No. 3,225,294 shows a sensing device using the application of eddy-currents and measuring the reaction. None of these devices results in a compactly constructed device which is easy to handle.
Other references, while not showing a device for measuring the small distance between two parallel surfaces, show a push button switch containing resiliently deformable elements. For example, French patent application No. 2,189,848 and German patent application No. 3,300,186 show a push button switch which is able to make several contacts sequentially in time while French patent application No. 2,441,259 and British PTO patent application No. WO84/03172 show a push button switch that can make several contacts at the same time.
It would be desirable to have a device for use in adjusting the distance between two parallel surfaces which is compactly constructed and is simple to handle.